Devices are commonly coated with thin films and other coatings in order to enhance their performance and functionality. Such coatings can be broadly characterized as being either hard coatings or soft coatings. Hard coatings, such as ceramic and diamond-like carbon, for example, are often applied to cutting tools to enhance their cutting ability and durability. Soft coatings, such as polymer-based materials, for example, are often applied to medical devices to improve their bio-compatibility.
For purposes of quality and process control, it is desirable to measure the toughness of the interfacial adhesion, or bond, between the coatings and substrates. Several testing methods are presently employed to measure interfacial adhesion toughness and include the “Pull” or “Stud Pull” test, the “Four-Point Bending” test, the “Tensile” or “Shear” test, the “Bulge” or “Blister test, the “Laser Impact Spallation” test, the “Indentation” test, and the “Scratch” test. However, there is often a lack of agreement in the measurements provided by these different techniques. Additionally, these techniques are not always effective at measuring the interfacial adhesion toughness of coatings applied to substrates having non-planar surfaces or flexible structures, particularly when the coatings comprise soft coatings.